Category Archives: Marshall Islands mathematics

Marshall Island Stick Charts

Imagine yourself on an island. Your toes are softly digging into the sand, you can taste the salt drying on your lips, and your hair is gently afloat due to the calm breeze. Next to you lies a slender canoe, ready to rock with the waves of the Pacific. The people you live with have given you a task to go to a nearby island in order make a peace treaty. Quite the daunting task. Looking out to the sea, all you see is blue. There are not any islands in sight. In your hands you possess a stick chart. This is the only tool you have to get to that nearby island.

An example of a Rebbelib Stick Chart. Image: Jason Eppink, via Flickr.

An example of a Rebbelib Stick Chart. Image: Jason Eppink, via Flickr.

I was interested in researching this tool more based on one of our group presentations. The stick charts were tools used strictly for navigation by the ancient/current people of the Marshall Islands. This country is made up of many small islands which are located in the Pacific Ocean, between Hawaii and Australia. It was fascinating to think about how people navigated the open sea without all of the technology we are comfortable with today.

There were three different kinds of stick charts that these Islanders found useful: Mattang, Meddo, and Rebbelib. They were all built out of sticks, coconut fibers, and shells. The shells were used to represent islands. The horizontal and vertical sticks were meant to be structural support, and the curved sticks represented waves or swells. Swells are wave patterns that have been made by distant weather. The local wind is not responsible for creating them. This means that they have consistent speed, direction, and are quite stable. These characteristics make swells predictable, which was a great help to the Islanders when they were making their stick charts. By studying the swell patterns and observing the far off weather and wind, the Islanders were able to navigate their boats.

Information on a stick chart had to be memorized because the Marshall Islanders were unable to carry a Mattang, Meddo, or Rebbelib, with them on their voyages. The differences between the three kinds are subtle. I learned that the Mattang was made for the specific purpose of teaching others how to navigate the waters around one island. The Meddo chart depicted only a few islands that were short distances away. These would be islands that the Marshall Islanders would have been familiar with and traveled to regularly. Thus the Meddo were meant for very particular voyages that were nearby.  While the Rebbelib, similar to Meddo, was a map that contained multiple islands and it mapped out further distances. Typically they would contain entire Island Chains. Island chains are large clusters of islands that can be scattered over a large distance. Another interesting fact about stick charts is that in general, they could usually only be read by the individual who created them.

In our scenario we are trying to get to one particular island, so I will focus Meddo stick charts. Meddo charts were unique in the fact they were meant to show the swell patterns relative to the position of various islands that were nearby. The Meddo charts did not take distance or direction into as much consideration as they did the swells. The Marshall Islanders were able to observe weather patterns and then apply that knowledge to how it would affect the water. The idea was that if they could understand these ocean patterns, then making their way from island to island should be easy. It was extremely important to them to display their stick charts in terms of the wind and weather rather than “North, South, East, and West,” like we do. The reflection and the refraction of the swells were much more important because that is what they would come in contact with when sailing.

Not only that, but they had some understanding of the consequences of sailing in deep versus shallow water. According to Ascher, “When waves move into shallow water, friction causes them to slow down. Depending on the ocean depth beneath it, a wave slows down differentially and so bends, eventually becoming more or less parallel to the underwater contours and, then, more or less parallel with the shoreline.” The Marshall Islanders had some understanding of this and it was also reflected in their charts.

These charts were vital to their survival and their communication with people on other islands. So think back to standing on the peaceful beach, preparing to go out in open waters. Do you think you could?

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